An alternative theory has been proposed, namely the ‘vitamin D trade-off hypothesis.’ According to this theory there is a decrease in vitamin D synthesis in the proximal renal tubules; decreased serum vitamin D levels result in loss of negative feedback on the parathyroid gland; decreased serum vitamin D levels also result in a decreased serum calcium level; an increase in serum parathyroid hormone (PTH) level occurs as a result of decreased serum vitamin D and calcium. | An alternative theory has been proposed, namely the ‘vitamin D trade-off hypothesis.’ According to this theory there is a decrease in vitamin D synthesis in the proximal renal tubules; decreased serum vitamin D levels result in loss of negative feedback on the parathyroid gland; decreased serum vitamin D levels also result in a decreased serum calcium level; an increase in serum parathyroid hormone (PTH) level occurs as a result of decreased serum vitamin D and calcium. |